David Avery is that the long lost twin to David Savery?!

Thanks guys👍

shouldn't there also be a statement to be made about conductor length? i.e. both conductors to take the same route or be the same length to ensure the load across the conductors is balanced?

In the land of Oz yes as long as each conductor is above 4mm2 follow the same rought and be the same size. Eg 3 X 300mm2 per phase

good to know!

Do they have to be close coupled together as Well

It's more complex for cables requiring OCPDs. For example a fault such as a nail penetrating only one of the parallel conductors may cause the whole let-though energy to be concentrated in that single cable, exceeding its k2S2 rating. See BS 7671 Appendix 10 for more info.

When selecting a position for a new Consumer unit is there a minimum "step back" for users or other Sparks to pull back out from the Unit?

PArallel the cables using a dual cable ferrule would be Ideal to my mind. (To make it easier for the next guy)

GOOD ONE JOE, COME ACROSS THIS ALOT, COMMON CASE: THE SUPPLY COMPANY. SEE IT EVEN IN NEWER BUILDS. MUCH EASIER WORKING WITH SMALLER CSAx2 THAN A MONSTER ANACONDA.

In Australia the requirement is that for conductors to be run in parallel they need to be a minimum of 4mm2 and to take the same route

A few years ago I went to connect a cooker up & the supply was 3 x 2.5mm twin & earth's from a 30 amp rewirable fuse, so 7.5mm then!

If you have an earth rod for house CU , hot tub CU, Garage CU, but are all connected back to main CU.... is this good or bad? Or is it best to split and run each as distribution and thus leave off RCD protection over the cables running to each?

Yes I've double up. 👍

Can you use parallel conductors to create the same cross-sectional area as a single one? Isn't that what the r1 + r2 over 4 calculation assumes?

Ive come across line and neutral conductors run in parallel, eg a five core SWA on single phase that had 2 cores for line, 2 for neutral and a single core and the armour for cpc. Would this be acceptable also? We simply replaced for more suitable 3 core SWA. Also if this possible, the calculations wouldnt simply 2 x 10mm2 as you'd have to calculate heat loss, volt drop, current carrying capacity etc.

Thank you for this info. To take the question a stage further. . . When running an SWA for a supply to an outdoor building requiring 10mmsq copper conductor for the earth, I could use 2 cores and the steel armour of a 4 core 4mmsq? There is a difference in resistance between the copper and steel conductors but enough for this to be a problem?

Joe may I ask you. Back in the days of rewireble fuses and some of them had cartridge fuses, it was common practice for your mum or dad to pull the fuse so as to place the fuse wire then replace it back into the fuse carrier, and it was never a problem. So why is said to be dangerous to pull the supply fuse,? When it is the same thing just bigger in size.

No. if one conductor fails that means a fire

A final ring circuit is much a parallel circuit is it no ?t, conductors are connected to the output of say, an MCB and take separate paths to to input terminals of a socket outlet. I would say that on a final ring circuit....one would expect as such but having stated that, two 6mm T&E cables feeding a say..9KW shower would not be expected from anyone following up the initial install, hence clear labelling would and should be a given. Issue could be that if one conductor lost connection or were broked for whatever reason is that the shower would only be fed with a 6mm conductor and with potentially no way of knowing that . Even if a MCB had tripped , and the reason for tripping was not evident, and there was no permanent short or otherwise, the consumer could just reset the MCB and be no wiser. As a retired and not a current 18th edition spark, last was 17th, my personal view is that albeit on paper it appears to be acceptable, it's not good practice, especially on a new circuit. I guess there are minor cost advantages if there is a current 6mm cable installed and there was a shower upgrade that required a larger cable that it could be tempting to save some money on the cost of a new cable, especially if a home owner nipped into B&Q and was intent on saving a few quid, but would that individual even test or label correctly, I think not. My view if I were to had taken on that job would be, use a 10mm as the cable still has to be run from the consumer unit to the shower switch and shower anyway, it's bad enought to fit a 10mm cable into switches/showers anyway, let alone 2x 6mm conductors, plus there is the increased potential for poor connections. Edited for smiles.....I am sure many sparks carrying out and EICR must have found that one 'leg' of a ring main has been 'lost' yet the customer has no knowledge of this fault as all will work as far as the consumer is concerned, and why would most consumers? or even have the knowledge of such things. As an apprentice, even a megger was a rare sight, I think the company I worked for with maybe 20/30 sparks may have had two and they spent very little time on sight and I was told I was the only apprentice who had asked for and AVO minor to be bought and deducted from my wages over a period of time. An MFT was not even a distant dream. Test lamps were a lampholder with a pygmy lamp and and two lengths of singles, continuity tester was a Freidland (I think) doorbell all taped up with a 6 volt torch battery and again, two short lengths of singles...if you found one with croc clips, you were posh ! No two way radios, I had two old phone handsets with a 9 volt battery and when working where there were a couple of spare cores in a cable..just twisted the whole lot in series for our communication. And may I just appologise to Lloyds Bank for re-purposing two of their old GPO phones for my own use 😂 I did again invest in a Drummond test lamp set from my meagre brown wage packet. The above is just my personal opinion and not intended to open up pointless bickering..open opinions, yes, debate yes, but please, not the usual armchair keyboard warriors.

Why does twin and earth not have dedicated green and yellow insulation on the earthing conductor by default?

maybe each wire should have a series fuse at that wires max rated current

In terms of doubling up.Adding a second core just adds another issue. That's two small cables which will look crap, possibly be awkward to terminate, either of which could fail and you're back where you started with a non compliant csa and a potentially dangerous situation in the event of a fault. I understand there would be a temptation with an upgrade to add another cable to share the new load or whatever ,but this practice in my view should be a last resort.

Your audio has gone very low

So are we saying that, say for example we couldn’t use a 10mm in parallel with a 6mm. (Different CSA’s) to make a 16mm conductor?

Confession time..I have an 8.4K shower in a home I own connected to a 6.00MM T&E cable, maybe up to 5m metres vertical trunking with less that 10% cable occupancy and a 5 metre horizontal run to the shower switch, above the loft insulation, connected to a 40 amp MCB. Its probably been like this for twenty years . I of course have checked connections and as to whether there are any signs of overheating on the cable and zero evidence whatsoever of any issues. Bearing in mind, other than like a cooker that could have a roast on for over an hour and some hob rings running for extended periods, the shower is rarely on for in excess of ten minutes so I would not expect to experience an issue. I am of course aware that one could say "what if someone left the shower on for an hour or even longer" ? This has prompted me to take my clamp meter and thermal image camera and carry out that scenario. The only answers to the above scenario can be..apart from replacing the cable with 10.0mm T&E a..Not ok b.. Ok Or words to that effect. From what I can gather, the 6.0mm cable installed in that method with a 40 amp MCB seems to be acceptable. load is (on paper) 37 amp and the cable installed in that method will accept in excess of 40 amp, posibbly as I just read up to 47 amp. I would not add an additional 6.0 mm cable connected in parallel to remedy, if at all a remedy was required. I would just rewire with a 10.00mm T&E, I may actually do that when it comes time to sell the property. Ether way, I am going to carry out some check as indicated above, just for kicks. Comments are welcomed of course.

surely parallel conducters are a safer way to install as in the event of a break you will still maintain 50% capacity on cpc not ideal but better than nothing on a single cable failure !

🤟🤟🤟

Why they have to be the shame I can’t put1x 6mm and one 10 example to archive 16mm?

This is about doubling up bonding conductors, don’t why so many comments about doubling up actual circuit supply cables.?

Doubling earth conductors to fulfill the requirement of having a thicker one.. OMFG 🤦🏻‍♂️ the apex of laziness

Would the lengths of combined conductors have to be the same along with the CSA? A ring main is effectively doubling up on conductors, is it not?